Before any player can play in the NFL they must be 3 years out of high school, sixth form in the UK.

As a result the vast majority of American football players go to college, our university, to play.

After their 3 year period is up the majority of quality players declare for the draft (some like being in college and stay, but that number is dwindling each year) and are available for the teams to select.

Now imagine a situation where instead of being punished by relegation for coming last, with potentially dire financial consequences, you are instead rewarded with the best player available at around 21 years of age. That is what the NFL does every year and will once again do tonight.

So if we were to crudely apply this to the Premier League, the bottom side - Cardiff at the moment - can pick up the best player in his age group that has declared for the draft.

Imagine the years that Messi, Ronaldo or Suarez had declared for the draft and ended up being snaffled by the Welsh club. "But why would Messi go to Cardiff?" is the obvious question, and a fair one; but the answer is essentially because he has to.

Players turning down teams has happened, but it is very rare indeed. The rationale behind this will become clearer as you read on.

So the NFL "rewards" the worst team each year with the ability to select the first player declared for that year's draft. The selections continue on to the second worst, third worst all the way to the previous Superbowl winner's selection before restarting with the same order again until each team has selected seven times (each new time the teams pick is referred to as a round).

Trading

. (Photo: Getty)

Teams cannot trade picks for money; only for actual players or, more commonly, for other draft picks.

For example, a couple of years ago Washington wanted to move up to second to select talented young quarter-back Robert Griffin III (above) from Baylor. Their need was in that position but they feared he could get snapped up by a rival, so they got trading...

The price that the team originally selecting second - St Louis - asked was:

Washington's first round pick that year (sixth overall)

Their second round pick that year

AND THEN their first round picks for the next TWO years. This means that both last year and this year St Louis had two picks in the first round, as described above.

In the NFL, the vast majority of players are acquired through the draft or via free agency (which is just like Bosmans in football).

A team cannot buy a player with money like in football, you can only trade for them with future draft picks or current players and due to its complexity, trading is reasonably uncommon.

Salary cap

Each team in the NFL must spend under $130,000,000 each season on player salaries and signing on fees.

Not only this but in the last CBA (Competitive Bargaining Agreement) between the players union and the league they agreed that the total spent on average by the teams must remain above 90%.

This keeps the league extremely competitive as no team can spend much more than any other. It all comes down to how well you coach, scout and ultimately find value purchases among players rather than who can spend the most - doesn't that sound refreshing football fans?

Building a team

.

So why is the draft perceived to be the way to build your team?

There are two main reasons; firstly because it is truly the only way to acquire a superstar in anything like his prime.

With a salary cap and rules against transfer fees you can't just buy a Cristiano Ronaldo equivalent even if you're the richest team in the world; you have to find him.

Once a team has a player of immense quality, the league is set up for that franchise to be able to keep him. There are rules which mean you can likely keep any player for the first seven years of his career without him having any real chance to leave.

With that sort of tie-in, the player often just signs longer-term deals that pay him high amounts more quickly and at a team he is settled at (contracts often pay higher salaries in the first few years, allowing teams to clear salary space if necessary).

The other way the draft is so important is that it is a way of acquiring starters for your team cheaply. Each position in the draft has a four or five-year contract assigned to it with no real negotiation; and the fees are reasonably low.

That means if you can find someone who will play for you regularly in the draft, then you give yourself more money to spend on other players - and given the competitive balance in the league it can be the difference between winning and losing.

Example:

Russell Wilson (Picked 75th in 2012) has been paid an average of $750,000 a season so far in his career and played as well as any Quarterback in the league.

This has left Seattle $129,250,000 to spend on the rest of their squad.

Given that several Quarterbacks in the league take $20,000,000 in salary and leave their team with only $110,000,000 to spend on their remaining 52 players, this is a considerable advantage for Seattle.

In fact this week it allowed them to sign another (formerly cheap) superstar in Richard Sherman on big money - something that wouldn't have been possible if they hadn't secured Wilson for relative peanuts.

Paul Kruger is a great example of both how the best teams handle the draft and their players, and why unless you really draft a superstar your drafting abilities are only useful for the first four-to-five years of a player's career - i.e. until they are due a new deal.

Kruger was chosen with the 57th pick of the 2009 draft by the Baltimore Ravens.

Kruger was a serviceable player while at Baltimore, but not a star. He averaged a salary of just $812,500 while at Baltimore which, considering the talent he had, was great value.

When his contract expired and he entered free agency the contract he desired was far above what Baltimore considered him worth; however Cleveland was happy to pay him ten times as much per year. Since then he's remained serviceable but instead of being great value for his team is more of a burden, cutting into the $130,000,000 available to spend.

This year's draft

. (Photo: Getty Images)

We got Ben Burrows to do a mock draft, which you can see here , as the best of the current college crop become up for grabs.

This year's talents that have made the biggest splash are Jadeveon Clowney, Sammy Watkins and quarter-back Johnny Manziel, but remember, the biggest, earliest drafts aren't always the best players.

The New England Patriots picked up a young Tom Brady with the 199th pick of the 2000th draft... and he's turned out okay.